The defining feature of tuberculosis is the long period of clinical latency during which the causative agent, Mycobacterium tuberculosis (Mtb), grows slowly if at all. It is difficult to overstate the importance of this quiescent behavior, as it likly underlies both the chronic nature of the infection and the relative ineffectiveness of antibiotics. Despite the growing recognition that quiescence is a relatively common microbial response to stress, the physiological state of these slowly- or non-replicating cells has remained enigmatic. To investigate the transition to quiescence, we identified both the genes required for the growth arrest and long-term survival of Mtb during stress-induced stasis, and the metabolic alterations that accompany this transition. Based on these complementary studies, we propose a regulatory cascade that senses host-derived stress, slows bacterial growth, and remodels metabolism for long-term stasis. In this project we will combine high-throughput genetic and biochemical methods to define the structure of this regulatory pathway and determine its ultimate role in promoting bacterial persistence and determining drug efficacy in vivo. We will then characterize the metabolic alterations that are required for the adaptation to quiescence and determine which of these are necessary for survival during stasis. Our goal is to devise new strategies to accelerate tuberculosis therapy through the identification and characterization of cellular pathways that are required for maintaining the quiescent state.